Neutrophil Elastase

What is the immune system

• complex, multi-layered network of cells, tissues, and organs

• Includes

  • white blood cells,

  • lymph nodes,

  • spleen

Role of the immune system

• defends the body against germs, toxins, and abnormal cells like cancer

Innate Immune System

• Innate = We are born with this

• general, immediate response

Adaptive Immune System

• Adaptive = Specific

• Develops over time through exposure to diseases or vaccines

• Creates tailored antibodies and memory cells to recognize and destroy specific pathogens quickly if they return.

Neutrophil Physical Description

• Innate immune cell

  • 12–15 um diameter

  • granular leukocytes

  • characterized by a multilobulated nucleus (3–5 lobes)

  • abundant antimicrobial granules in their cytoplasm.

Neutrophil Function + Origin

• the most common white blood cell (40%–60%)

• act as the body's first line of defense against infection, particularly bacteria.

• Produced in the bone marrow and, when activated, move from the bloodstream to tissue to engulf microbes

Neutrophil Phagocytosis

• engulf pathogens and cellular debris into an internal vesicle called a phagosome

• a membrane-bound intracellular vesicle formed by phagocytes (e.g., macrophages, neutrophils)

• Used to engulf and destroy pathogens, cellular debris, and foreign materials

Neutrophil Degranulation

• Release preformed antimicrobial proteins and enzymes from cytoplasmic granules into the extracellular space or phagosomes to destroy pathogens

NET formation/release

• Trapping, immobilizing, and eliminating a spectrum of pathogens

• including gram-positive and gram-negative bacteria

• acid-resistant bacteria, fungi, protozoa, and influenza viruses

NET Components

• a scaffold of decondensed DNA

• decorated with histones and antimicrobial proteins derived from neutrophil granules.

  • myeloperoxidase (MPO) - catalyzes the creation of highly reactive oxidants—mainly hypochlorous acid (bleach)—to kill bacteria, fungi, and viruses

  • Calprotectin - chelating essential metals which starves bacteria and fungi

  • Neutrophil elastase - A serine protease

What are enzymes

• End in -ase

• a biological catalyst, usually a protein

• Speeds up specific chemical reactions in living organisms without being consumed

• Work by lowering the activation energy needed for reactions to occur

What are proteases

• an enzyme that catalyzes proteolysis

• Breaks down proteins into smaller polypeptides or single amino acids by hydrolyzing peptide bonds

• Examples:

  • stomach-based pepsin for digestion

  • pancreatic trypsin and chymotrypsin in the small intestine

  • Blood-clotting enzymes thrombin and plasmin

What are Serine Proteases

• Family of enzymes that use a specific serine residue as a nucleophile in their active site to catalyze hydrolysis

• The main player in the catalytic mechanism in the serine proteases is the catalytic triad.

• The triad is located in the active site of the enzyme, where catalysis occurs

• Triad consists of:

  • Histidine

  • Serine

  • Aspartic Acid

Other Serine Proteases in NETs

• cathepsin G (CG)

• Proteinase 3 (PR3)

What is obesity

• Obesity occurs when caloric expenditure in the body decreases

• Most of the energy is stored in fat cells as triglycerides.

• Triglycerides continue to accumulate in adipocytes, which limits blood flow in adipose tissue, and the oxygen supply is reduced as a result

• intestinal mucosal permeability increases

Obesity and FFA Stress

• State of chronic low-grade free fatty acid (FFA) stress by causing an excessive release of FFAs into the blood from enlarged (hypertrophic) adipose tissue, which exceeds storage capacity.

• Obese adipose tissue becomes dysfunctional, failing to store lipids efficiently, which leads to increased outflow of FFAs into circulation.

  • Chronic elevation causes "lipotoxicity," creating systemic insulin resistance, oxidative stress, and chronic low-grade inflammation.

Viral Infection and NETosis

• COVID-19 is a trigger for NETosis because it is a virus

NETs and Obesity

• lipid stress and abnormal lipid remodeling induce NETosis.

• High levels of cholesterol

• specific oxidized lipids

• lipid-related metabolic changes (such as those in obesity)

• act as stressors that activate neutrophils, leading to the formation of Neutrophil Extracellular Traps (NETs)

Pulmonary Fibrosis

• Excessive release of NETs contributes to the pathogenesis of COVID-19, exacerbating inflammation, thrombosis, and tissue damage

• Can lead to pulmonary fibrosis via neutrophil-fibroblast crosstalk

Adverse effects of pulmonary fibrosis

• shortness of breath, coughing, and reduced lung function

• Can lead to cannula/ventilation

• Severe can cause death

My project overview

• Obesity is a major risk factor for severe COVID-19, significantly increasing the likelihood of hospitalization, ICU admission, and death.

• Individuals with obesity are about 34% more likely to become infected after exposure and have higher risks of mortality

• Because obesity is a chronic state of low-grade inflammation, neutrophils are more prone to activation.

• This increased neutrophil reactivity and neutrophil extracellular release could be the cause of more severe COVID-19 infection in individuals with obesity.

Significance of Neutrophil Elastase to My Project

• Neutrophil Elastase is a marker of neutrophil extracellular trap release

• I can look at it as an indicator of neutrophil activation in response to an environment of increased FFA stress and viral infection.